Mobile communication devices, such as computers, cellular telephones and the like, are typically powered by power cells, i.e. rechargeable electrochemical cells often also referred to as batteries. In order to recharge the power cells such devices are generally provided with a charger unit for connecting to a power jack socket on the device which is wired to contacts with the terminals of the cells. The charger itself usually consists of a plug box containing a step-down transformer and an AC-DC converter or rectifier which is wired to a connecting plug. When in use, the plug box is plugged into a 120V or 240V mains socket and the connecting plug is coupled to the device. The wire trailing between the device and the plug box can be unsightly. Moreover, if the trailing wire is snagged or jerked the wire and connectors may be damaged, as indeed could be the socket or the wall. Furthermore, the device may be pulled to the ground.
Chargers are bulky items to carry around. Therefore most users of compact portable equipment such as cell phones and the like do not carry chargers with them, but prefer to rely upon periodic charging, perhaps overnight. Often users rely on even more infrequent charging. As a result cells often run down at inconvenient times when no charger is available.
Inductive battery charger systems are known such as the system described in U.S. Pat. No. 7,164,255 to Hui incorporated herein by reference. In Hui's system a planar inductive battery charging system is designed to enable electronic devices to be recharged. The system includes a planar charging module having a charging surface on which a device to be recharged is placed. Within the charging module, and parallel to the charging surface, is at least one, and preferably an array of primary windings that couple energy inductively to a secondary winding within the device to be recharged. The disclosure also provides secondary modules that allow the system to be used with conventional electronic devices not formed with secondary windings.
Hui's system provides an inductive charging platform for mobile telephones. However, unless the device to be charged has an integral secondary winding coil, it may be necessary to carry a bulky secondary module with which to use the platform. Hui's system does not describe any convenient means for providing secondary windings for conventional devices.
There is therefore a need for a convenient power supply for a mobile communication device and particularly for a charger, which may be conveniently retrofitted to conventional devices.